1. Field of the Invention
The present invention relates to a fuel container having high gasoline barrier properties.
2. Description of the Related Art
In recent years, coextrusion blow-molded containers made of plastic materials are preferably used for containers for storing fuels, such as gasoline, and examples for such containers are the fuel tanks of motor vehicles. As for the plastic material used as the material of such containers, there are high expectations in polyethylene (especially very high-density polyethylene) with regard to economic efficiency, molding processability, mechanical strength, and the like. However, it is known that fuel tanks made of polyethylene have a disadvantage that the stored liquid gasoline and/or the vaporized gasoline easily permeates through the polyethylene walls into the atmosphere.
To eliminate this disadvantage, a method is known in which a halogen gas (e.g. fluorine, chlorine, or bromine) or sulfur trioxide (SO3) or the like is blown into the polyethylene container, and the inner wall of the container is halogenized or sulfonated. Another method that is known is to obtain a container that has a multilayered structure and is made of a polyamide resin layer and a polyethylene resin layer (see Japanese Laid-Open Patent Publication No.6-134947, U.S. Pat. No. 5,441,781). Yet another method that is known is to obtain a container that has a multilayered structure and is made of an ethylene-vinyl alcohol copolymer (EVOH) resin layer and a polyethylene resin layer (see U.S. Pat. No. 5,849,376 and EP 759359). Furthermore, a fuel tank is known, which has a multilayered structure and includes an inner layer, an outer layer, and a layer with gasoline barrier properties (i.e., a barrier layer), and in order to enhance the gasoline barrier properties, the barrier layer is arranged closer to the inner layer (see Japanese Laid-Open Patent Publication No.9-29904 and EP 742096).
However, in the manufacture of fuel containers according to these methods, the gasoline permeation amount cannot be suppressed sufficiently. Recently, there are strong demands with respect to the economic consumption of gasoline and the protection of the environment, and there is a strong demand for the reduction of the gasoline permeation amount in fuel containers.
A first fuel container of the present invention is a coextrusion blow-molded fuel container having a container body made of a layered structure, the layered structure comprising: a barrier layer made of a barrier resin (A); and an inner layer and an outer layer made of a thermoplastic resin (B) that is different from the barrier resin (A); wherein a ratio (X/Y) of a distance (X) between end portions of the barrier layer at a pinch-off part of the fuel container and an average thickness (Y) of the container body is at least {fraction (1/10000)} and at most {fraction (1/10)}; and wherein a ratio (Y1/Y) between a total thickness (Y1) of the layers of the container body that are located on the inside with respect to the barrier layer and an average thickness (Y) of the container body is at least {fraction (3/10)} and at most {fraction (7/10)}.
In a preferred embodiment, a ratio H/L between a height H of the pinch-off part and a width L of the pinch-off part of the container is 0.1 to 3.
In a preferred embodiment, a MFR (MFRbarrier) of the barrier resin (A) and a MFR (MFRinside) of a resin constituting an innermost layer of the container satisfy the following relation:
8xe2x89xa6MFRbarrier/MFRinsidexe2x89xa6100xe2x80x83xe2x80x83(1)
wherein MFRbarrier and MFRinside denote values measured at 190xc2x0 C. under a load of 2160 g, and if the melting point of the resin is about 190xc2x0 C. or higher, then the measurement is carried out under a load of 2160 g at a plurality of temperatures above the melting point, inverses of the absolute temperatures are marked on the horizontal axis and the logarithm of the MFR is plotted on the vertical axis in a semi-logarithmic graph, and the MFR is determined by extrapolation to 190xc2x0 C.
A second fuel container of the present invention is a coextrusion blow-molded fuel container made of a layered structure, the layered structure at least comprising: a barrier layer made of a barrier resin (A); and an inner layer made of a thermoplastic resin (B) that is different from the barrier resin (A); wherein a cutting face of a pinch-off part of the container is covered by a barrier member made of a barrier material (C).
A third fuel container of the present invention is a fuel container made of a layered structure, the layered structure at least comprising: a barrier layer made of a barrier resin (A); and an outer layer made of a thermoplastic resin (B) that is different from the barrier resin (A); wherein the fuel container is provided with an opening through its body, wherein a cutting face of a layer at the opening is covered by a barrier member made of a barrier material (C), and wherein the layer covered by the barrier member is located on the outside with respect to the barrier layer.
A fourth fuel container of the present invention is a fuel container made of a layered structure, the layered structure at least comprising: a barrier layer made of a barrier resin (A); and an outer layer made of a thermoplastic resin (B) that is different from the barrier resin (A); wherein the fuel container is provided with an opening, a cut-out or a groove is provided at an outer surface of the fuel container around the opening, and the cut-out or the groove is covered or filled with a barrier member made of a barrier material (C).
In a preferred embodiment of the third and fourth fuel container, a pinch-off part of the fuel container is covered with a barrier member.
In a preferred embodiment of the third and fourth fuel container, a component for fuel containers is mounted onto the opening portion.
In a preferred embodiment, the component for fuel containers is a barrier member made of the barrier material (C), and the cut-out or groove is covered by attaching the component for fuel containers.
In a preferred embodiment, the cut-out or groove provided in the outer surface around the opening completely surrounds the opening.
In a preferred embodiment, a depth of the cut-out or groove is 0.1 to 0.8 times an average thickness (Y) of the container body.
In a preferred embodiment, a depth of the cut-out or groove is at least 0.2 and less than 1 times a total thickness (Y2) of layers locating on the outside with respect to the barrier layer.
In a preferred embodiment, a width of the cut-out or groove is 0.01 to 5 times an average thickness (Y) of the container body.
In a preferred embodiment, a ratio (Y2/Y) of total thickness (Y2) of layers located on the outside with respect to the barrier layer and the average thickness (Y) of the container body is at most {fraction (45/100)}.
In a preferred embodiment, the barrier member covers the cutting face, cut-out or groove via an adhesive.
In a preferred embodiment, a gasoline permeation amount (measured at 40xc2x0 C. and 65% RH) of the barrier material (C) is at most 0.1 times a gasoline permeation amount (measured at 40xc2x0 C. and 65% RH) of the thermoplastic resin (B).
In a preferred embodiment, a gasoline permeation amount (measured at 40xc2x0 C. and 65% RH) of the barrier material (C) is at most 400 gxc2x720 xcexcm/m2xc2x7day.
In a preferred embodiment, the barrier material (C) is at least one selected from the group consisting of metal foil, epoxy resin, polyvinylidene chloride resin, polyvinylalcohol resin, polyamide resin, polyester resin, and fluorocarbon resin.
In a preferred embodiment of the second to fourth containers, the container comprises: an intermediate layer serving as the barrier layer; and an inner layer and an outer layer made of the thermoplastic resin (B).
In a preferred embodiment, an adhesive resin layer is located between the barrier layer and the layer made of the thermoplastic resin (B).
In a preferred embodiment, the fuel container comprises at least one recovered layer.
In a preferred embodiment, a gasoline permeation amount (measured at 40xc2x0 C. and 65% RH) of the barrier resin (A) is at most 100 gxc2x720 xcexcm/m2xc2x7day.
In a preferred embodiment, the barrier resin (A) is at least one selected from the group consisting of polyvinyl alcohol resins, polyamides, and aliphatic polyketones.
In a preferred embodiment, the thermoplastic resin (B) is a polyolefin.
In a preferred embodiment, the thermoplastic resin (B) is high-density polyethylene.
Therefore, the present invention described herein makes possible the objectives of: providing a fuel container having high barrier properties with respect to the fuel, for example gasoline, contained in the container; providing a blow-molded fuel container which sufficiently suppresses fuel permeation at a pinch-off part of the container, and in which the pinch-off part has sufficient contact strength, resulting in an excellent impact resistance; and providing a fuel container that effectively suppresses the fuel permeation at a bonding portion at which a component is attached to the container.